Although there are many Chinese elements, I'm inclined to believe that it is Tibetan, at least stylistically. Apart from the Tibetan script, other elements in the picture point to this. For instance, the fiery beast around the zodiac is not a dragon, but King Mara. It is a play on a Buddhist Wheel of Life, which are popular in Tibetan Buddhist art. The same goes for the circle on the bottom right. Here is a piece that I own:

Also, the three figures in the top resemble various Tibetan Buddhist deities. The top looks like some kind of a Tara (see here). The figure on the bottom left looks like Vajrapani. Here is another piece that I own:

In addition, the symbols between the two bottom circles are found in a book I have seen on recurring symbols in Tibetan art. The phurba dagger in the middle is the most obvious.

The Encyclopedia of Tibetan Symbolsand Motifs says that this is called the "Golden Tortoise Diagram." Legend states that the Bodhisattva Manjusri inscribed the essence of his religious knowledge on the belly of a golden tortoise.